Robot-guidance assembly for providing a precision motion of an object

ABSTRACT

There is provided a robot-guidance assembly for providing a precision motion of an object, especially for providing a precision motion of a disklike member such as a wafer, including a robot having at least one robot arm. The at least one robot arm has a free end and a fixed end. The robot can move the free end of the at least one robot arm in at least one moving plane. The assembly also includes a guiding apparatus for precisely guiding the free end of the at least one robot arm in the at least one moving plane. There is also provided a method for inspecting a surface of an object.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a robot-guidance assembly for providing aprecision motion of an object, an inspection tool for inspecting asurface of an object, and a method especially carried out in such aninspection tool according to claims 1, 14 and 15.

2. Description of Related Art

Semiconductor wafers are produced by complicated multi-step processes ina clean room environment. The production of sophisticated electronicchips from wafers may include as many as about 150 steps. Technologiesin the submircon range are very delicate, and there always exists achance of error or malfunction at each of the many stages, which oughtto be discerned as soon as possible.

Throughout the semiconductor processing precision motion systems, e.g.positioning stages, are used, for example in wafer metrology tools likemicroscopes.

The common approach is to use a self contained, i.e. a functionallyindependent, x-y-motion system within the metrology tool, which has achuck to which the wafer is transferred from the wafer handling systemthat includes a robot for transporting the wafer from one to the nextproduction or inspection stage.

This results in the typical workflow:

-   -   1. The x-y-motion system moves to a load position, at which the        wafer is    -   2. transferred from the robot on to the chuck of the x-y-motion        system, after this the wafer is moved into the metrology tool        and the    -   3. metrology or inspection process is carried out, in the        following    -   4. the motion system moves the wafer back to the load position,        where it is    -   5. transferred to the handling system or robot.

Looking at this flow from a systems standpoint one can see that thereare two redundant motion systems, i.e. the handling system and thex-y-motion system of the metrology tool. In this kind of handling systemthe throughput depends strongly on the time the metrology tool has towait for material handed over by the robot handler. Moreover, it shouldbe noted that in the state of the art systems two separated motionsystems are necessary for the handling and the metrology process.

These and other disadvantages have lead to the objects of the presentinvention, especially to simplify the known motion systems, and toincrease the throughput of the production and/or inspection processes.

SUMMARY OF THE INVENTION

The inventive solution is obtained by the apparatus defined in theindependent claims. Further refinements and advantageous developmentsare part of the respective dependent claims.

Thus far, in general, the invention is a robot-guidance assembly forproviding a precision motion of an object, especially for providing aprecision motion of a disklike member like a wafer, comprising robotmeans including at least one robot arm encompassing a free end and afixed end being attached to the robot means, wherein said robot isadapted to move said free end of said arm at least in one moving plane,whereby guiding means adapted to and provided for precisely guiding saidfree end of said arm in at least said plane is provided.

In this way, for the first time, the invention sets forth thepossibility to use the robot that is present in every wafer handlingsystem as a motion system for metrology tools as well, canceling theneed for an extra motion system within the metrology tool. In a highlyadvantageous manner, this cuts down costs and also reduces cycling timefor a measurement of the wafer due to the time saved for thenon-existing wafer transfer from the handling system to the metrologymotion system. Additionally it should be noted that for the presentinvention various types of handling robots like scara or linear robotscan be applied.

Depending on the motion system of the robot, i.e. whether the robot hasa polar co-ordinate system with a linear-radius- or r-moving-axis and arotary-stage- or theta-moving-axis (r-theta), or whether it has aCartesian co-ordinate system for a x-y-motion, it is provided that theguiding means favorably comprises one or two or even more precisionmoving or guiding axis. Thus it is guaranteed that the end of the robotarm or an end-effector means, which is attached to the end of the robotarm for accepting and holding the object or the disklike member at thisend, is forced to move exactly along the respective axis, whereby,otherwise, the movement of the end-effector would fail the precisionrequirements for a scan inside, for instance, a microscope. In case of ar-theta-system generally one axis of motion is sufficient. When ax-y-motion-system is used two stacked linear axis are provided. Thedirection of motion for these axis is off-set by 90° giving a Cartesianco-ordinate system.

The choice of the motion system has also an impact on the selection ofan appropriate end-effector means. Therefore, for instance, according tothe invention, if, for example, a scara robot with a r-theta motionsystem is used, it is provided that the end-effector favorably has thecapability to rotate the disklike member about its rotary axis. Such anend-effector is disclosed by WO 02/02282 A1 which is hereby incorporatedby reference.

Thus, highly advantageous, the end-effector replaces the movement of aseparate rotary stage, which would be necessary otherwise. Moreover,this allows that the dependency of the angular orientation of the wristjoint and thus that of the end-effector of a scara robot can becancelled quite easily. The mentioned dependency originates from thefact that the end-effectors of those robots are always oriented radiallywith respect to the theta axis.

Another further development of the invention relates to the provision ofa flexible mounting mechanism for removable mounting the end of therobot arm and/or the end-effector means to said guiding means.Preferably, the mounting mechanism comprises a pneumatic lock which isarranged on one side or upper side of a stage, whereas the other side ofthe stage comprises sliding means. The sliding means can includebearings of any known kind, e.g. crossed roller bearing, profiled guideswith recirculating ball carriages or even air bearings. These slidingmeans co-operate with rails arranged on a mounting member for thepurpose of precisely guiding the stage, and thus the end of the robotarm or end-effector.

Further more, the inventive mounting mechanism, if at wish, encompassesa rotational degree of freedom, that allows to rotate the end-effectorinto a locking position, which also opens up the possibility to cancelthe dependency of the angular orientation of the wrist joint and thusthat of the end-effector as described above.

According to a preferred embodiment of the invention the inventiveguiding means passively guides said free end of said robot arm. Thismeans that only the robot means provides the driving force for themovement of the guided free end of the robot arm and/or theend-effector, respectively. This includes that merely the motors and theposition feed back elements of the robot are used for the motionprocess.

For a even further refinement of the motion system of the inventiveassembly the guiding means comprises additional encoders for a secondarypositioning feedback system. Thus, by using a closed-loop control of thestage position, there is no chance that the stage will become lost.Precision motion system in this regard means that the stage is guided ina tolerance band of 2 to 3 μm per 100 mm.

Of course, it is possible that the guiding means itself includes aninternal drive. In this case, for example, the robot can be used as amotion controller using its internal feedback system for to close theposition control loop. Advantageously, thus there is no need for anadditional interface to the process controller. Moreover, it simplifiesthe control programming since the robot and the metrology motion systemuse the same control language.

Moreover, according to an additional further development of theinvention, it is provided that the guiding means includes a selfcontained motion system, as it is known from XYZ-stages of microscopes,wherein means are given which allow, especially a mechanical uncouplingof the end-effector completely from the robot arm. It should be notedthat also in this embodiment the robot plays an important roll. In thisrespected, for instance, the robot can still supply the rotatingmovement of the disklike member or wafer on an appropriate end-effector(see above) and the control electronics, thus reducing costs andsimplifying the system design. The energy supply however is provided viathe locking mechanism.

It is another object of the invention to provide an inspection tool forinspecting a surface of an object, especially for inspection a surfaceof a disklike member like a wafer comprising an inspection device forinspecting the object, and an assembly as described above forpositioning and aligning the object within the inspection device.

Moreover, the scope of the invention extends to a method, particularly,carried out in the inventive inspection tool, wherein an end-effector ofa robot, holding a disklike member or wafer, at a defined position, isattached to a guiding means comprising motion axis which on a drivenmovement of said guiding means leads to a movement of said end-effectorto and inside the inspection tool such that a surface inspection scancan be carried out of said disklike member, whereby after the inspectionthe end-effector is moved back to the defined position. In that positionthe end-effector is detached from the guiding means, whereby after thedetachment the robot with its end-effector can move to the next stationin the production or inspection process.

BRIEF DESCRIPTION OF THE DRAWING

The invention together with additional features and advantages thereofwill be best understood from the following description.

It is shown:

FIG. 1 an over view of the essential parts of the inventive robotguidance assembly.

FIG. 2 a sectional view A-A (see FIG. 4) of one embodiment an inventiveend-effector lock or locking mechanism.

FIG. 3 a sectional view of the position fixing element use by thelocking mechanism according to FIG. 2.

FIG. 4 a top view of the locking mechanism of FIGS. 2 and 5.

FIG. 5 sectionals views B-B (see FIG. 4) of the embodiment of FIG. 2 ofthe inventive locking mechanism, whereby FIG. 5A shows the mechanism inthe locked position and FIG. 5B shows it in the unlocked position.

FIG. 6 shows the inventive assembly built in a rack.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of one embodiment of the inventiverobot-guidance assembly 1. The assembly comprises two main components,namely a robot body 2 and guiding apparatus or means 3. The robot 2shown is a SCARA type robot. It includes a body 4, a robot arm 5 and anend-effector 6 which holds a wafer 7. The robot body 2 includes motordrives for driving the robot arm 5 and the end-effector 6, and a robotcontroller, both not shown in FIG. 1. End-effector 6 is used to grab andhold wafer 7, and robotic arm 5 including various motors and mechanicalmechanisms not shown in the Figures, moves end-effector 6 and the waferthat it holds within its grasp 7 from one station to another in theinspection or production process.

For the handling of single wafer in an Semiconductor Fabric robot 2typically has three positioning axis's. One axis to move the wafer 7with its arm vertically up and down, called z-axis, and at least twoother axis's to move it horizontally from one station to another in theproduction process, typically a Theta and an R-axis. These types ofrobots are well known in the art and are not further describedhereinafter in detail.

According to the embodiment of FIG. 1 the end-effector 6 is attached tothe guiding apparatus 3 via and end-effector lock 8. The guidingapparatus to this end is a linear guide which is part of a metrologytool (not shown in FIG. 1). It comprises a stage 9 to which at its topthe mating partner of the end-effector lock 8 is attached to. At thelower side of the stage linear slides 10 are provided. These slides 10,as a moving and guiding partner, co-operate with a pair of parallelrunning rails 12 which are arranged on a plate 11. The slides 10 can beof any known kind including crossed roller bearings, profiled guideswith recirculating ball carriages or even air bearings. From thefunctional point of view the linear guide 3 shown in FIG. 1 is a passiveguide, which forces the end-effector 6 on a straight line providing aprecise, robot 2 driven linear movement of the end-effector 6 inside ametrology tool like a microscope (not shown), whereby it is guaranteedthat the surface of the wafer 7 during movement remains in a definedorientation in space.

Yet for a complete scan, i.e. for to reach every point on the wafersurface with respect to a stationary outside view point inside themetrology tool a single linear motion is not sufficient. According tothe invention with respect to the embodiment displayed in FIG. 1 thisproblem is solved by using an end-effector 6 with the capability torotate the wafer 7 grasped about the symmetry axis of the wafer whichincludes a 90° angle with the surface. Such an end-effector 6, forinstance, is disclosed in the WO 02/02282 A1 which is herebyincorporated by reference. The application of such an end-effector 6even further has the advantage that there is no need any longer for astand alone pre-aligner because the end-effector 6 is able to pre-alignthe wafer while moving it from one station to another.

Another essential part of the inventive assembly or guiding means 3 isthe end-effector lock or locking mechanism 8 as already mentioned above.A detailed view of a possible embodiment according to the invention canbe seen in FIG. 2. The locking mechanism 8 is a kinematic mount in formof a pneumatic lock which removable combines the stage 9 with theend-effector 6, thereby interlocking the end-effector 6 with the stage 9by charging the pneumatic lock with negative pressure. A negativepressure lock is especially favorable in a clean room environment.

The locking mechanism 8 includes three essential parts, namely a stageplate 13 which is affixed to the stage 9, a locking member 14 comprisingthe major parts of the lock 8, which will be described in detail below.The locking member 14 is attached to the end-effector plate 16 which islodged to the underside of the end-effector housing 15 (FIG. 1), wherebythe mating surfaces are supposed to be precision flat. The end-effectorplate 16 is fixed to the locking member 14 via screws which are to beinserted into screw-holes 17 extending through the end-effector plateand which find their end in pocket holes of the locking member 14.

The locking member together with the end-effector plate form a hollowmember 18. The hollow member 18 is divided into an upper and an lowerchamber 18′, 18″ by the membrane 19. The membrane 19 air-seals the twochambers from one another. At the center of the locking member a hollowguide 20 is provided. The hollow guide 20 is part of the locking memberand comprises a through hole 20′ which moveably accommodates conelocking pin 21. At its lower end pin 21 pushes through membrane 19 andcomprises plates 24′ and 24″, that forms hard center 24, whichsandwiches membrane 19. In this respect plate 24″ lies inside chamber18″ and plate 24′ inside chamber 18′.

In its lower part cone locking pin 21 includes a blind hole 23, whereinthe upper part of the spring 22 is brought in. Spring 22 attaches thebottom of blind hole 23 and is supported by the end-effector plate 16.In case the locking mechanism is not charged with negative pressurespring 22 holds the cone locking pin in an equilibrium position; as itis shown in FIG. 2.

Hollow guide 20, at the upper end of locking member 14, is surrounded bylocking ring 25 which is embedded in a groove that is brought in at thetop side of locking member 14. The thickness of the ring 25 levels withthe upper side of locking member 14 with the exception that at the innerside of locking ring 25 a ring nose or edge 26 is provided which extendsout of the surface. The outer diameter of edge 26 is the same as theinner diameter of stage plate hole 27. Thus edge 26 centers stage plate13 into the locking position of the locking mechanism 8. Stage platehole 27 together with cage members 29 of hollow guide 20 form cages forlocking balls 28. For this embodiment, all together, there are threelocking balls at a distance of 120°.

Moreover a position fixing mechanism 31 is provided. It comprises threeposition fixing elements. These elements 31 are arranged at the outerring of locking member 14 (see FIG. 4) on its upper side, and are thussandwiched between the upper side of locking member 14 and stage plate13. The position fixing elements include blind holes, wherein pins 32are inserted. The blind holes are formed by key notches 33 in the uppersurface of locking member 14 at a distance of 120° (see FIG. 4), wherebythe orientation of the notches is the same as that of locking balls 28or cage members 29, and by channels within the lower side of stage plate13, whereby these channels are arranged next to notches 33.Functionally, it is the purpose of the position fixing mechanism 31 toprovide a defined orientation between the locking member 14 and thestage plate 13 in the assembled state of the inventive locking mechanism8.

With regard to the function of the inventive locking mechanism 8 it isnow referred to FIGS. 5A and 5B. FIG. 5A displays lock 8 in its lockedposition. In this case chamber 18″ is pressurized. Thus an upwardmovement of cone locking pin 21 is achieved. In its up position the coneof cone locking pin 21 pushes cage members 29 aside. This in turnpresses locking balls 28 down onto edge 26 of locking ring 25, wherebyin this way stage plate 13 is locked to locking member 14.

The other way round is shown in FIG. 5B. Therein it can be seen that itis not chamber 18″ but chamber 18′ that is charged with negativepressure, thereby cone locking pin 21 is pushed down and opens the lock8.

The inventive locking mechanism favorable allows to mount theend-effector 6 into a repeatable position, as well as an exactlyrepeatable orientation in space, thus guaranteeing that the wafersurface 7 is always parallel to the direction of the linear guide. Ofcourse, the invention is not restrict to pneumatic locks as describedabove but can be also of a electro mechanic or magnetic kind. Note thateven gravity could be sufficient.

FIG. 6 shows the inventive assembly build in a rack 34. Rack 34comprises on its front a Load Port for FOUP's, i.e. a front openingunified pod 35, and on its back the inventive guidance 3 for preciselyguiding the end of robot arm 5 and the end-effector 6, respectively.Thus far, the inventive guidance 3 replaces a conventional XY-stage onwhich normally robot 2 has to place wafer 4 for any kind of purpose. Ofcourse it could be provided that the rack 34 as a whole or at least theinventive guidance 3 are vibration-isolated.

1. A robot-guidance assembly for providing a precision motion of anobject comprising: a robot including at least one robot arm that has afree end and a fixed end, wherein said robot moves said free end of saidat least one robot arm in at least one moving plane; and a guidingapparatus for precisely guiding said free end of said at least one robotarm in said at least one moving plane.
 2. The assembly according toclaim 1, wherein said guiding apparatus includes at least one guidingaxis.
 3. The assembly according to claim 1, further comprising anend-effector at said free end for accepting and holding said object. 4.The assembly according to claim 3, wherein said end-effector rotatessaid object about an axis that is perpendicular to a surface of saidobject and intersects a midpoint of said object.
 5. The assemblyaccording to claim 3, further comprising a mounting mechanism formounting said free end of said at least one robot arm and/or saidend-effector to said guiding apparatus.
 6. The assembly according toclaim 5, wherein said mounting mechanism rotates said end-effector intoa locking position.
 7. The assembly according to claim 5, wherein saidguiding apparatus includes a stage having two sides, and wherein saidmounting mechanism is attached to one of said two sides.
 8. The assemblyaccording to claim 7, wherein said stage includes slides at a lower sideof said stage.
 9. The assembly according to claim 8, wherein saidguiding apparatus includes a mounting member having guide rails thatco-operate with said slides.
 10. The assembly according to claim 1,wherein said guiding apparatus passively guides said free end of said atleast one robot arm.
 11. The assembly according to claim 1, wherein saidguiding apparatus includes encoders for a positioning feedback system.12. The assembly according to claim 1, wherein said guiding apparatusincludes an internal drive.
 13. The assembly according to claim 3,wherein said end-effector is removably mounted to said free end of saidat least one robot arm.
 14. An inspection tool for inspecting a surfaceof an object comprising: an inspection device for inspecting saidobject; and an assembly according to claim 1 for positioning andaligning said object within said inspection device.
 15. A method forinspecting a surface of an object comprising: holding a disklike member,having a surface, at a defined position with an end-effector of a robot;removably connecting said end-effector to a guiding apparatus thatincludes a motion axis, activating said guiding apparatus, to preciselymove said end-effector to and inside an inspection tool along at leastone moving axis.
 16. The method according to claim 15, furthercomprising moving said end-effector back to said defined position afterinspection, wherein in said defined position the end-effector may bedetached from said guiding apparatus.
 17. The assembly according toclaim 1, wherein said object is a disklike member.